TEHRAN, Iran (CNN) -- Legal action must be taken against Iranian opposition leader Mehdi Karrubi for claiming post-election detainees were being raped behind bars, said the governor of Tehran province, as hard-line criticism grew against the reformist.

Reformist Mehdi Karrubi faces mounting criticism from hard-liners.

"If such a person has made such accusations that have infuriated the people and it is shown that he cannot prove them, then legal steps must be taken with regards to this person," said Gov. Morteza Tamaddon, according to the Iran Labor News Agency.

Tamaddon similarly said he and parliamentary representatives visited Evin on Tuesday, adding that the detainees "maintain that they have not been abused in any way."

Tamaddon and other senior officials have suggested that Karrubi should be investigated and even prosecuted for making allegations of rape. Others, such as Iran's powerful parliamentary speaker Ali Larijani, have demanded that Karrubi offer evidence and witnesses to back up his claims.

Ayatollah Hossein Taeb, commander of the Basij militia that attacked protesters after the disputed June 12 elections, has purportedly called for Karrubi to be flogged 80 times. CNN could not independently confirm Taeb's remark, which was posted on the Web sit of the reformist Etemad-e Melli newspaper.

That newspaper, which is aligned with Karrubi, was shut down by Iranian authorities Sunday for publishing "unlawful and criminal material," state-run media reported, though details about the materials in question were never revealed.

The hard-line criticism against Karrubi started earlier this month when he openly described the mistreatment of detainees arrested in the aftermath of the Islamic republic's presidential election, and called for an investigation into prison conditions.

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Karrubi and fellow reformist candidate Mir Hossein Moussavi ran against hard-line President Mahmoud Ahmadinejad, who was declared the overwhelming winner and was recently sworn in for his second term.

"Some of the former detainees have told of such brutal and violent, repeated rapes of the young women [in detention] that have caused irreparable damage to their reproductive systems," Karrubi said on his party's Web site on August 8. "Others have raped our detained young men with such brutality that they [the victims] have been afflicted by depression and are no longer speaking with anyone and refuse to leave the dark corners of their houses."

He added that an investigation would "teach a lesson to the thugs and criminals in the future and prevent the smearing of the reputation of the Islamic Republic."

Larijani dismissed the allegations, calling them "sheer lies," saying a special panel of Iran's parliament, or Majlis, conducted a "precise and comprehensive inquiry" into the treatment at Tehran's Evin prison, and found "no cases of rape or sexual abuse," Press TV reported.

He challenged Karrubi to "present evidence of such outrages" for the Majlis to investigate, according to Press TV.